A senior U.S. envoy says Washington believes that North Korea is increasingly unwilling to live up to its nuclear disarmament commitments, and is using three detained Americans as pawns.

Glyn Davies, the U.S. special representative for North Korea policy, told reporters in Beijing on Monday that North Korea's unwillingness to release the three Americans is an impediment to resuming disarmament talks.

He said North Korea is drifting further away from its obligations to denuclearize. North Korean Foreign Minister Ri Su Yong told the United Nations General Assembly over the weekend that his country's nuclear program is not "a bargaining chip," but is needed to guard against U.S. hostility.

Davies met with his Chinese counterpart Wu Dawei to discuss how to bring North Korea back to disarmament negotiations.